X-Git-Url: https://git.kernel.dk/?a=blobdiff_plain;f=arch%2Fpowerpc%2Finclude%2Fasm%2Fbook3s%2F64%2Fmmu.h;h=a809bdd77322783d4109be90ef0d888fdcf682df;hb=6161a37307f3320808b5a7549593b991500f2656;hp=1ceee000c18d7e6b9efc84a831c2c4ebc915405a;hpb=85f78456f286da46fb054c7d45e4193cb757ac83;p=linux-2.6-block.git

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index 1ceee000c18d..a809bdd77322 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -35,6 +35,21 @@ typedef pte_t *pgtable_t;
 
 #endif /* __ASSEMBLY__ */
 
+/*
+ * If we store section details in page->flags we can't increase the MAX_PHYSMEM_BITS
+ * if we increase SECTIONS_WIDTH we will not store node details in page->flags and
+ * page_to_nid does a page->section->node lookup
+ * Hence only increase for VMEMMAP. Further depending on SPARSEMEM_EXTREME reduce
+ * memory requirements with large number of sections.
+ * 51 bits is the max physical real address on POWER9
+ */
+#if defined(CONFIG_SPARSEMEM_VMEMMAP) && defined(CONFIG_SPARSEMEM_EXTREME) &&  \
+	defined(CONFIG_PPC_64K_PAGES)
+#define MAX_PHYSMEM_BITS 51
+#else
+#define MAX_PHYSMEM_BITS 46
+#endif
+
 /* 64-bit classic hash table MMU */
 #include <asm/book3s/64/mmu-hash.h>